In his first major deal since taking over from Mark Tucker in September, Thiam has been on a major charm offensive with investors since announcing the audacious – and some say expensive – takeover on 1 March. The rights issue – the biggest ever to take in place in London – is scheduled to be formally launched on Wednesday, the eve of the election – which threatens to unsettle the stock market.

The accompanying prospectus is likely to contain information about how AIA, which was in the process of being floated out of the taxpayer-rescued insurance giant AIG when Pru tabled its bid, has been trading. Pru will be trying to deflect criticism that surfaced at the time the deal was announced for buying a business less profitable than its own operations by demonstrating that, under international accounting rules, – rather than US ones – its performance is better.

City investors will also be looking for signs that Pru has taken steps to cut the $1bn in fees it is paying banks and lawyers involved in the transaction, which may make them more inclined to back the cash call. The insurer must be able to put up a convincing argument, as it needs 75% of shareholders to vote for the transaction later this month. The high threshold has sparked some speculation that the hurdle may be difficult to achieve, particularly when it emerged that Capital had been trying to find a way to stop the bid.

An analyst at Capital, Patrice Collette, approached Pru's rival Aviva and acquisition-hungry Resolution about formulating a break-up bid for the Pru, but this was rejected.

Pru has appeared relaxed about the rebel shareholder, particularly because while Capital as a group controls 12% of the shares, the part of the operation over which Collette has influence is far smaller.

Banks advising on the deal are expected to price the rights issue on Tuesday, and indications suggest that against Friday's close of 579p, the new shares could be priced at about 120p on the basis of four new shares for six existing shares.